Colin Creevey
Some of the younger years weren't all that adept at taking orders from a student who had just turned into a fox, so Colin took it upon himself to play crossing guard to get kids from Gryffindor tower to the tunnels. He had expected his petulant younger brother to whine about the command, but to obey.
But Dennis was not in the fire brigade of innocent Gryffindors exiting the tunnel. Horrified with the way his thoughts immediately ran to the worst possible scenarios, Colin sprinted up several flights of stairs to try and spot the wayward sibling. As he approached the seventh floor, he heard a sinister voice liken an unseen figure to a house-elf.